Channel 4 is cutting the length of the majority of Dispatches shows from an hour to 30 minutes, but is pledging to maintain its budget by running more episodes.

The broadcaster will air 40, rather than the current 30 Dispatches next year in a bid to ensure "a near constant presence in the schedule".

According to the Channel 4 chief creative officer, Jay Hunt, the overall programming budget for Dispatches will remain the same. The series will continue to air at 8pm on Mondays.

The Channel 4 head of news and current affairs, Dorothy Byrne, said research showed that viewers wanted "faster, more reactive content".

"With 40 shorter programmes a year we can expand the range of subjects we cover and increase topicality," she said.

Kevin Sutcliffe, the editor of Dispatches and Channel 4 deputy head of news and current affairs, said that next year the broadcaster would look to offer independent producers the chance to produce Dispatches episodes in blocks of eight to help them generate more revenue.

Sutcliffe also announced a £250,000 fund for an "investigative journalism training scheme" saying there has been a decline in the pool of investigative journalism since "the demise of training grounds such as World in Action". The scheme will offer training for 20 journalists over two years.

Hunt added that bringing on new investigative journalists and independent producers was important because "we're staring down the barrel of not having a supply base".

When challenged about shortening the length of most Dispatches, Byrne – who has argued in the past for longer, rather than shorter current affairs films – said Channel 4's research showed that viewers often found an hour was too long for some subjects.

Byrne added that viewing habits have changed and that she had assurances from Hunt that hour-long slots were still available on Channel 4, should the subject warrant it.

Speaking at a Channel 4 briefing about changes to its current affairs output in London on Tuesday, Byrne said: "I don't know how many will be an hour. But I believe we'll get the hour when we need it. That satisfies me. I don't think we need an hour for every subject, but we do for some others."

In 2007 she said that former BBC1 controller Peter Fincham's decision to cut Panorama from 45 minutes to half an hour on a Monday night, rather than an hour-long slot on Wednesday because of ratings, was "unjustifiable".

However, Byrne argued Dispatches' case was different: "I think Panorama went through a very lightweight period. It's not just about length, it's about whether your subject matter is good."

She said the reduction in episode length would "not change the nature of our journalism".

Channel 4 News presenter Jon Snow said the BBC's decision to cut Panorama from an hour was "an act of wanton disregard… we're now in a different age".

Hunt said that budgets for an hour-long episode of Dispatches will range from about £140,000 to £180,000, while half hours will range from about £90,000 to £110,000.

Channel 4 also revealed two new ideas being developed for news and current affairs, which will allow viewers to use their remote controls to edit their own versions of Channel 4 News and view the show's archive.

In addition, Hunt said that foreign affairs series Unreported World will probably not remain on a Friday night, but added that it will be moved to "a prominent slot".

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